The present invention relates to actuator support structures for use in disc drive data storage systems. More specifically, the present invention relates to an attachment between a flex lead or other electrical circuit supporting structures and an actuator arm.
Rotating disc drive data storage systems include one or more discs which may be rotated about a vertical spindle axis. Each disc typically has a plurality of concentric tracks on one or both disc surfaces from which information is read or onto which information is written by means of reading and/or writing transducer head assemblies. A plurality of support arms form a configuration known in the art as an "E-block", "rotary arm", or "actuator arm". A first end of each support arm is attached to and supports at least one magnetic head carrying arm and a corresponding transducer head assembly. Usually, each support arm is attached to two magnetic head carrying arms configured such that a transducer head assembly is positioned adjacent to each disc surface in the data storage system. A second end of each support arm is connected to a central portion of the rotary arm, wherein lies the axis of rotation of the rotary arm. An actuator coil provides the necessary torque to rotate the arm about this axis to move the transducer head assemblies over the magnetic discs to desired track locations.
As the transducer head assemblies read information from or write information to the tracks of the magnetic discs, electrical signals are transferred between the transducer head assemblies and an electrical circuit which may be positioned remote from the rotary arm. Because of the dynamic movement of the rotary arm, a flexible circuit, known as a flex, a flex cable or a flex lead, is used for transferring the electrical signals to and/or from the transducer head assemblies. The flex cable is typically a multi-layer cable made of plastic or other readily available flexible materials with thin copper runs included for carrying signals. The flex cable may simply be used as a circuit for carrying signals from the transducer head assemblies to an external circuit. However, the flex cable can also support external circuit components which may be wire bonded onto the flex cable itself.
As disc drive data storage systems continue to reduce in size, available space for attachment of flex leads to the rotary arm is reduced as well. Additionally, new magnetoresistive (MR) transducer head assembly designs require additional wires or electrical connections for each transducer head assembly. This in turn requires a more dense layout of the flex cable to accommodate the additional runs necessary. Consequently, room for attachment of the flex cable to the arm is becoming increasingly small.
Previously, a screw was used to attach the flex cable to the rotary arm. Mounting flex cables or other electrical circuit supporting structures such as circuit boards to the rotary arm with a screw has several disadvantages. First, mounting the flex cable to the rotary arm introduces certain manufacturing and assembly difficulties. As stated above, space on the flex cable for mounting to the rotary arm is very limited. Therefore, the screw itself must be very small. Use of a screw requires that a tapped hole be placed in the rotary arm for receiving the screw. Also, the designs of many rotary arms provide very limited access for driving the screw into the rotary arm with a screw driver. The small size of the hardware, the limited vertical access, and the requirement that a tapped hole be placed in the rotary arm all provide obvious manufacturing difficulties.
Another disadvantage of using a screw to secure the flex cable or other electrical supporting structures to the rotary arm relates to grounding of the rotary arm assembly. One known method of grounding the rotary arm assembly, grounding the rotary arm through the bearings of the spindle, results in intermittent grounding. The intermittent grounding is a result of intermittent contact between the bearings and the rotary arm caused by obstructions such as grease on the bearings. A non-grounded or intermittently grounded rotary arm assembly can result in increased noise in the electrical signals communicated or processed between the transducer head assemblies and an external circuit.
Another method of grounding the rotary arm assembly uses the screw which mounts the flex cable to the rotary arm to provide an electrical ground connection from a ground run on the flex cable. However, this method of grounding the rotary arm assembly has disadvantages as well. Subjecting the rotary arm to variations in temperature can result in the screw loosening. As the screw loosens, the ground connection can be lost. Consequently, current methods of attaching the flexible cable to the rotary arm and of grounding the rotary arm are less than ideal.